Voltage regulator and failure circuits



April 22, 1969 D. v. CARMODY 3,440,492

VOLTAGE REGULATOR AND FAILURE CIRCUITS Filed sept. 1, 196e United States Patent Omee 3,440,492 VOLTAGE REGULATOR AND FAILURE CIRCUITS Doyle V. Carmody, Milan, Tenn., assignor to International Telephone and Telegraph Corporation, New York, N.Y., a corporation of Maryland Filed Sept. 1, 1966, Ser. No. 576,674 Int. Cl. H02h 3/28 U.S. Cl. 317-27 7 Claims This invention relates to voltage regulators and particularly to voltage regulators incorporating failure detection and protection circuits.

Prior art voltage regulators, failure detectors and protective devices as applied in the telecommunications art have depended generally on combinations of conventional rectifers, voltage dividers, fuzes, relays and the like. None of these have been entirely satisfactory since they have lacked failure monitoring and switchover as well providing uncertain voltage levels, tooslow response times, required excessive time for resetting, or the like.

It is, therefore, a primary object of this invention to provide an improved voltage regulator which incorporates features of a failure detector and protection circuit such that it is capable of providing a source of stable voltage while assuring safety and providing warnings in case of failure or partial failure of components in the regulator or in the load.

The foregoing object and others related thereto will be more fully understood from the following description when read in connection with the accompanying drawing which shows a schemat' diagram of a preferred embodiment of the invention.

Turning now to the figure for a detailed description of the preferred embodiment of the invention it will be noted that the figure i-s divided into two parts, one on either side of the vertical dashed line. This vertical line divides the drawing into two nearly identical portions. The portion to the left of the vertical line represents a primary, or principal, voltage regulator and protective device. The portion to the right represents a secondary or stand-by regulator. The stand-by regulator is coupled tol the primary regulator in such a way that failure of a component in the primary regulator will automatically cause the stand-by regulator to function.

Turning lirst to a description of the left hand side of the figure voltage regulation is provided by operation of the Zener diodes D1 and D2. The diodes are shown connected serially from a voltage -V applied on the terminal 6 through the resistor R3 and the contacts of relay R1 to ground at terminal 13. Resistor R3 functions as a dropping resistor and in a preferred embodiment of the invention consisted of a 20 ohm resistor which will drop the voltage -V which is set at 50 volts by approximately 24 volts while the two Zener diodes provide a drop of about 13 volts apiece. As a consequence of the operation of these components, the potential at the first load point 3 in the example is maintained at -26 volts, while that at load point is maintained at -13 volts. These two potentials are made available at terminals 11 and to communication systems or control devices indicated by the block 2S, labeled Load Circuits.

The voltage supplied at terminal 3 is monitored by a bridge circuit including the elements CRI, CRZ, CRS, CR4 and a winding of relay R1. The opposite terminal of the bridge at point 7 is initially set at a voltage equal to one half of V which is established by the potential of -V at terminal 4 and a voltage divider made up of equal sized resistors R5 and R6 which in a preferred embodiment have a resistance of 500 ohms each. So long as the potential supply from terminal 3 is nearly equal to that at terminal 7 the bridge will remain in balance and the 3,440,492 Patented Apr. 22, 1969 relay R1 will remain inoperative. However, should either diode D1 or D2 short, the -1/2 V volts would become 1A V volts by operation of the remaining Zener diode. With 1A V volts, or `13 volts,

insure complete operation.

When the relay R1 operates it will open the break contacts R1 which are shown closed in the ligure and close the corresponding make contacts. Operation of the R1 contacts will cause a transfer of the load to the stand-by regulator shown to the right of the dashed line. The stand-by regulator will be seen to be identical in its principal components to the original regulator and will function in the .same fashion.

Assuming again that the conditions illustrated in the figure prevail and that one of the original Zener diodes D1 or D2 suddenly becomes open, the potential supplied to the number 3f terminal will rise to about -S V (or 37 volts) causing an unbalanced condition on the bridge circuit. This in turn will cause the R1 relay to operate changing the position of the make-break contacts R1 so that the stand-by regulator will again be placed in control of the potentials to the load circuit.

As indicated previously, the stand-by regulator functions in essentially the same way as the primary regulator. For example, when the make-break contacts R1 are operated by the relay R1, terminals 7 and 9, shown as being connectable to a load (not shown), are disconnected from the voltage sources at terminals 3 and 5 and connected instead to the terminals 17 and 23. The voltage available on terminals 17 and 29 are made equal to those provided at respective terminals 3 and 5 by the diodes D3 and D4 in conjunction with a resistor R4 supplied by a potential -V at terminal 26. The same values of resistance and identical diodes may be used n the standby regulator so that it exactly replaces the primary regulator when needed.

If, after the stand-by regulator assumes control of the load voltages there is a failure of either D3 or D4, unbalance will be produced in the bridge circuit associated with this second regulator. This situation will provoke operation of the relay R2 to switch the make and/or break contacts R2 to their alternate positions, disconnecting the potential -V at terminal 26 from the load terminals 11 and 15 and supplying a signal to an alarm circuit (not shown) over terminals 21. The alarm can be a relay operating a visual signal, an aural signal or some other indicator.

It `will be apparent from the -iigure that in the event of failure in the diodes D1 or D2 the primary fail lamp 9 will be lighted through the application of voltage at terminal 8 through the contact R1 to ground. Likewise, if there is a failure of the secondary or stand-by regulator the secondary fail lamp 19 will be operated over the terminal 28 and the corresponding make contact R2.

While the scribed above applications, it is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What is claimed is:

1. A voltage regulator incorporating a protection and warning circuit, comprising:

a first terminal upon which a voltage is applied,

a second terminal at ground potential,

means for dividing lsaid voltage into two lower voltages for supply to a load circuit,

principles of the invention have been dein connection with specific apparatus and said means including a resistor and two Zener diodes said means responsive to imbalance of a bridge circuit coupled in series between said ifirst terminal and said includes means for supplying a signal'to operate an second terminal, alarm in the event of failure of said second voltage means supplying a reference potential, regulator. a bridge circuit connected to sense one of the tiwo lower 6. A voltage regulator substantially as claimed in claim voltages and compare it with said reference potend 5, in which: tial, and said means responsive to imbalance of a bridge circuit means responsive to imbalance in said bridge circuit to includes means for disconnecting said regulator from disconnect said two lower voltages from said load said load circuit. circuit. 7. A voltage regulator substantially as claimed in claim 2. A voltage regulator substantially as claimed in claim 1, in which; 1, in which: said means responsive to imbalance in said bridge cirsaid means responsive to imbalance in said bridge incuit includes means to operate a light indicating cludes a relay having break contacts for disconfailure of the voltage regulator. nectin-g said two lower voltages from said load circuit, References Cited 1, Avg/gage regulator substantially as claimed in claim UNITED STATES PATENTS said means supplying a referencepotential includes a 3,160,805 12/ 1964 Lawson.

source of voltage and a voltage divider. 3,214,705 10/ 1965 Smith et al. 307-318 X 4. A voltage regulator substantially as claimed in claim 3,340,435 -9/1967 Hoel 317--27 X 1, in which:

a second Voltage regulator essentially identical to that OTHER REFERENCES of claim 1 is made available Silicon Zener Diode and Rectifier Handbook, Motorsaid means for disconnecting said two lower voltages ola, Inc., second edition, July l0, 1961, p. 73.

from said load circuit includes means for connecting said second Voltage regulator to said load circuit, and JOHN F. COUCH, Primary Examiner.

said second voltage regulator includes means for sup- I. D' TRAMMELL Assistant Examneh plying desired voltages to said load circuit.

S. A voltage regulator substantially as claimed in claim 4, in which: U.S. C1. X.R.

the second voltage regulator includes means respon- SW1-23, 64, 86, 318; 317-31; 323-22 sive to imbalance of a bridge circuit, and 

1. A VOLTAGE REGULATOR INCORPORATING A PROTECTION AND WARNING CIRCUIT, COMPRISING: A FIRST TERMINAL UPON WHICH A VOLTAGE IS APPLIED, A SECOND TERMINAL AT GROUND POTENTIAL, MEANS FOR DIVIDING SAID VOLTAGE INTO TWO LOWER VOLTAGES FOR SUPPLY TO A LOAD CIRCUIT, SAID MEANS INCLUDING A RESISTOR AND TWO ZENER DIODES COUPLED IN SERIES BETWEEN SAID FIRST TERMINAL AND SAID SECOND TERMINAL, MEANS SUPPLYING A REFERENCE POTENTIAL, A BRIDGE CIRCUIT CONNECTED TO SENSE ONE OF THE TWO LOWER VOLTAGES AND COMPARE IT WITH SAID REFERENCE POTENTIAL, AND MEANS RESPONSIVE TO IMBALANCE IN SAID BRIDGE CIRCUIT TO DISCONNECT SAID LOWER VOLTAGES FROM SAID LOAD CIRCUIT. 